OER Parts offers a wide selection of Heater Parts for your 1976 GMC All Models. OER Parts offers 1976 GMC All Models Blower Motor, 1976 GMC All Models Heater Box, 1976 GMC All Models Heater Control Valves, 1976 GMC All Models Heater Cores. 1976 GMC All Models Hoses and Parts, 1976 GMC All Models Vent and Duct Parts.